The present invention relates to an industrial vehicle that includes a hydraulic actuator, which is driven by hydraulic pressure, and a hydraulic pump, which is driven by an engine to generate hydraulic pressure.
A forklift is one example of a known industrial vehicle that includes an engine, a hydraulic pump driven by the engine, and a hydraulic mechanism, which is configured to operate a hydraulic actuator by hydraulic oil from the hydraulic pump. A forklift includes, for example, a hydraulic lift cylinder, which serves as a hydraulic actuator that lifts and lowers a fork, and a hydraulic tilt cylinder, which serves as a hydraulic actuator that tilts a mast. When driving the hydraulic pump with the engine, an increase in the load applied to the hydraulic pump may result in insufficient engine torque and cause the engine to stall. Japanese Laid-Open Patent Publication No. 2012-62137 describes a structure that prevents such an engine stall. The engine may also stall when a plurality of hydraulic actuators are operated at the same time.
In the above patent publication, a discharge pipe opens when a decrease of the engine speed is detected. This causes the engine speed to further decrease from when the discharge pipe opens to when the load on the hydraulic pump decreases. Thus, an engine stall may still occur.